Я просто поменяю токен сессии, в config/initializers/secret_token.rb
:
# Your secret key for verifying the integrity of signed cookies.
# If you change this key, all old signed cookies will become invalid!
# Make sure the secret is at least 30 characters and all random,
# no regular words or you'll be exposed to dictionary attacks.
MyAPP::Application.config.secret_token = 'ABC123'